Condensed heterocyclic derivatives to be used in the present invention (hereinafter referred to as condensed heterocyclic derivatives) are compounds disclosed in e.g. Japanese Unexamined Patent Publications No. 264489/1988, No. 76487/1986, No. 250388/1989 and No. 289573/1990. These compounds are known to have high herbicidal activities against weeds in upland fields and paddy fields and high selectivity for crop plants such as soy bean and corn. When such condensed heterocyclic derivatives are to, be used as herbicides at upland fields or paddy fields, they are formulated into wettable powders or suitable formulations such as granular wettable powders, emulsifierable concentrates or flowables, which will be diluted with water for application.
Generally, an agricultural chemical is desired to be highly active at a low dose, and various methods have been studied for improving the activities of agricultural chemicals. For example, a composition containing a product obtained by co-pulverization of an agricultural chemical compound and a water-soluble polymer compound (Japanese Unexamined Patent Publication No. 308202/1989) and a composition containing a residue obtained by distilling a solvent off from a solution having an agricultural chemical compound and a water-soluble polymer compound dissolved in inorganic solvent (Japanese Unexamined Patent Publication No. 211504/1989) have been disclosed.
At the time of applying a herbicide, an excess amount of the active agent is applied in many cases to obtain adequate effects. However, it is undesirable to apply a large amount of the active agent from the viewpoint of the economical burden on farmers or possible dangers to the safety to human and animals and environmental pollution. An agricultural chemical composition is desired which is free from phytotoxicity to crop plants and which is capable of providing adequate effects in a less amount of the active agent used.
If the above-mentioned water-soluble compound is incorporated for the purpose of improving the herbicidal effects of a thiadiazabicyclononane derivative, it is likely that during the storage, the thiadiazabicyclononane derivative undergoes decomposition, whereby not only it is impossible to obtain the herbicidal effects of the original compound, but also phytotoxicity to crop plants may result in some cases.